400 AUTOGAMY. 



table, taken from Loew, contrasts alpine and sub-alpine plants in regard to the- 

 relative prevalence of autogamy: — 



(I.) Of 130 entomophilous plants in sub-alpine regions — 

 35 species = 26"9% are rarely or never autogamous. 

 86 species = 66'1% are autogamous as well as heterogamous. 

 9 species = 6"9% are invariably or usually autogamous. 



99-9% 



(II.) Of 133 entomophilous plants in high alpvie regions — 

 35 species = 26"3% are rarely or never autogamous. 

 78 species = 58"6% are autogamous as well as heterogamous. 

 20 species = 15'0% are invariably or usually autogamous. 



99-9% 



Thus we see that 20 high alpine species show pronounced autogamy as compared 

 with 9 sub-alpine forms. 



In the mountain Flora of Scandinavia the prevalence of autogamy is even more 

 marked. 



(III.) Of 74 species from the Dovrefjeld — 



12 species = 16 "2% are rarely or never autogamous. 



40 species = 54'0% are autogamous as well as heterogamous. 



22 species = 29'7% are usually autogamous. 



99-9% 



As compared with the high alpine plants (table II.) we note a diminution of 10°/^ 

 in those which are always heterogamous, and an increase in those usually auto- 

 gamous of some 15°/g. 



In plants whose distribution is restricted to the Arctic regions, the number of 

 autogamous plants is in the majority. 



(IV.) Of 45 species of purely Arctic plants — 



species = 0*0% are almost exclusively heterogamous. 

 14 species = 31"1% are autogamous as well as heterogamous. 

 26 species = 57"8% are usually autogamous. 



5 species=ll'l% are doubtful. 



100% 



Precisely what factors in their environment have led to this increased preval- 

 ence of autogamy in high alpine and far northern species is at present not certainly 

 determined. A lack or comparative rarity of insect-visitors on the one hand, or 

 unfavourable climatic conditions on the other, might either of them well lead to 

 such a condition. Regarding the alleged paucity of insects in the Alps, one so well 

 qualified to speak as Hermann Müller says^: — " I have not been able to convince 

 myself that alpine flowers are, on the whole, less frequently visited and crossed by 

 insects than are those of the plain". Nor does Loew, with the statistics before him, 

 dissent from Müllers opinion. So also with regard to the northern types, concern- 

 ing which the view is widely spread that their preponderating autogamy is connected' 



^ Alpeyihluvie.i, p. 547. 



